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The crystals of pentafluoropropionylbenzoylmethylene triphenylphosphorane thatbears two strongly electron-withdrawing groups in alkylidene moiety are monoclinic and its spacegroup is C2/c,with α=11.271(3),b=18.253(6),c=23.938(7),β= 91.09(2)°,z=8.TheX-ray diffraction intensity data were collected on a four-circle diffractometer.The structure hasbeen solved by direct method and refined by block-diagonal least-squares method.The final R-index was 0.075 for 3146 independent observed reflexions.In this paper the structure of this ylideis compared with that of corresponding arsonium ylide previously reported.Both ylidic skeletonstructures are planar with sp~2 hybridization.The bond length of P-C(1)is 1.748(5) with bond order.1.60 while the bond order of As-C(1)in the corresponding arsonium ylide is 1.46,indicating thatthe phosphonium ylide has a greater contribution of“ylene”structure to the overall structure.Asa result the phosphonium ylide should be less reactive than the corresponding arsonium ylide.Inboth ylides,the major delocalized canonical forms of negative charge are shown to be 3.
The crystals of pentafluoropropionylbenzoylmethylene triphenylphosphorane that bears two strongly electron-withdrawing groups in alkylidene moiety are monoclinic and its space group is C2 / c with a = 11.271 (3), b = 18.253 (6), c = 23.938 (2) °, z = 8.TheX-ray diffraction intensity data were collected on a four-circle diffractometer. The structure has been solved by direct method and refined by block-diagonal least-squares method. The final R-index was 0.075 for 3146 independent observed reflexions. This paper the structure of this ylideis compared with that of corresponding arsonium ylide previously reported. Both ylidic skeletons are planar with sp ~ 2 hybridization. The bond length of PC (1) is 1.748 (5) with bond order .1.60 while the bond order of As-C (1) in the corresponding arsonium ylide is 1.46, indicating that the phosphonium ylide has a greater contribution of “ylene ” structure to the overall structure. Asa result the phosphonium ylide should be less reactive than the correspondin g arsonium ylide. Inboth ylides, the major delocalized canonical forms of negative charge are shown to be 3.